Commercial warewashers commonly include a housing area which defines the washing and rinsing area for dishes, pots pans and other wares. A conveyor is used to transport the wares through the warewasher from an input side to an output side. At the output side of the warewasher a ware receiving table/trough may extend several feet to allow cleaned wares to exit from the warewasher completely before being removed by kitchen personnel.
U.S. Pat. No. 6,550,607 describes a warewasher including a conveyor drive arrangement including a jam detection system. The warewasher includes a conveyor drive arrangement including a drive motor assembly formed by a drive motor and reduction gear box, with the rotational axis of the assembly being substantially upright. The drive motor assembly includes a rotating output shaft. A rotatable slip clutch includes an input side operatively connected for rotation by the drive motor assembly output shaft, and an output side operatively connected for driving a dog-type conveyor. Specifically, the output side is connected with an upright shaft that extends to a crank arm. As the crank arm rotates in a clockwise direction (looking from top to bottom along the rotational axis) it repeatedly engages a drive block. The dog-type conveyor moves racks containing wares through the machine on tracks in a stop and go fashion with every rotation of the crank arm. The dogs are attached to a cradle that is suspended below the tracks on plastic slider blocks. The cradle is made to oscillate back and forth in the direction of arrow by the rotating crank arm and drive block, propelling the racks forward on every forward stroke of the cradle by way of the dogs engaging with webs on the bottoms of the racks. The drive block runs in a channel. During the reverse stroke of the cradle, the cradle dogs disengage from the rack webs (pivoting downward as they contact other webs on the reverse movement) and the racks remain stationary (commonly referred to as dwell time) until the next forward stroke of the cradle. In this arrangement, on average racks moved through the warewasher are generally stationary for the same duration of time that they are moving forward. That is, the rack must hesitate while the conveyor is returning to the drive position flooding some of the rack wear with wash and rinse water. During the driving of the rack, some ware is washed with a lesser amount of water. To overcome this lower amount of water, the wash and rinse system is designed to meet dish cleanliness criteria during the movement of the rack. The system is “over washing” the ware during the long stops as a result meaning that the wash and rinse system could be more efficient if a conveyor system with less dwell time were designed.
It is more effective to push/pull the racks through the warewasher at a more even rate (e.g., less stationary time) to ensure more even water distribution to the wares.
Several designs were considered for a constant motion conveyor system including a stainless steel drive chain and a chemical resistant belt. The stainless drive chain would do a fine job moving the rack but the current cost to implement such a system in a conveyor machine would be several times more expensive than that of a ratcheting conveyor. Corrosion resistant plating on a carbon steel chain would be available at a lesser cost but the long-term reliability would be an issue as the plating wore off the chain, which would lead to rust. The belt design is lower cost but belt materials do not currently exist at this time that can withstand the chemicals, heat, and hold tension in the machine to meet quality and reliability standards.